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Aug. 9, 1949.
s. B. CRARY
2,478,622
REGULATOR SYSTEM '
Filed June I, 1946
1T0 SYSTEM mencouuecnou
F‘icg, i.
5
5
POSITIVE
_
PHASE.
SEQUENCE
NETWORK
51"";
3
U
D:
O
y.
Inventor:
Selden B. Gray,
SPEED-
Zsup -
by
His Attorheg.
Patented Aug. 9, 1949
r 2,478,622
vUNITED STATES PATENT OFFICE
2,478,622
REGULATOR SYSTEM
Selden B. Crary, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York
_
1
Application June 1, 1946, Serial No. 673,731
14 Claims. (01. 322-24)
2
My invention relates to regulator systems and
more particularly to improvements inautomatic
voltage regulator systems for synchronous
generators.
A further object of my invention is to pro
vide automatic regulating means for an induc
tion motor driven exciter set for limiting the
loading of the exciter as a function of the exciter
In the last twenty years there has been a
set speed.
signi?cant trend to the unit-type of synchronous 6
In accordance with my invention, I have pro
generator station wherein each generating unit
vided a means for limiting the load on the induc
is self suiiicient with respect to its electrically
tion motor driving the exciter to a value con—
and steam driven auxiliaries including the ex
sistent with the maximum power availability of
citation means for the alternating current
the induction motor for any given value of
generator. It has been customary to provide a
terminal voltage on the motor. The maximum
direct connected exciter for the synchronous
torque of the induction motor is essentially a
generator because of the increased reliability of
predetermined function of its slip for a given
. such means of excitation.
However, the direct
terminal voltage, and, if the exciter voltage, and
connected exciter introduces additional di?icul
ties into the design and operation of such gen
15 consequently the power it will supply to the
alternator ?eld and the load it will place upon
erating units.
One method of providing excitation for the
the motor drive, is limited so that the slip of the
induction motor drive does not increase above
synchronous generator now increasing in favor
a value corresponding to its pullout or maximum
for the higher speed units is the use of an in 20 torque, the reliability of the motor driven ex
duction motor driven exciter set in which the
citer set will be improved and the generator will
induction motor is supplied power from the main
not lose synchronism with the system as a re
A.-C. system to which the local synchronous
sult of failure of its excitation source due to an
generating unit is connected. With the use of
abnormal decrease in speed of the exciter set.
present type automatic voltage regulators, dur 25 I provide apparatus for measuring the exciter
ing a system disturbance causing the alternator
set slip in terms of frequency by comparing the
terminal voltage to decrease, the voltage regu
generator frequency with a frequency propor
lator will attempt to maintain normal terminal
tional to the motor speed, this apparatus in
voltage on the alternator to prevent loss of syn
chronism, and will force the ?eld excitation '
thereby applying an increased exciter load on
the induction motor drive at a time when its
input voltage is low. Under these conditions of
low input voltage and heavy exciter load, the
induction motor will be overloaded and cannot
maintain speed, and if the disturbance remains
cluding a tachometer generator and a Selsyn
receiver which functions to give a variable volt
age and frequency proportional to the value of
the slip of the induction motor. This slip pro
portional voltage is compared with a standard
reference voltage and upon reaching a certain
' predetermined value slightly less than the maxi
mum value of slip that can be tolerated without
for any appreciable length of time and is of
pullout of the motor, the excess voltage is applied
sumcient severity, the slip of the induction motor
to an operating coil of the voltage regulator in
drive will increase until the maximum torque
a direction to oppose the tendency ofthe regu
point is reached, after which the motor will slow 40 lator to continue forcing the exciter voltage to
down and excitation of the alternator will be
higher values. This effectively prevents the
almost completely lost, resulting in possible loss
voltage regulator from forcing the exciter to ex
of synchronism of the main generator and fur
cessive load values thereby increasing the slip
ther aggravation of the system disturbance. This
of the induction motor drive, and prevents over
has resulted in the use of oversize induction 45 loading of the induction motor to a point where
its maximum torque is reached and alternator
motors and their. resulting ine?iciency under
normal operating conditions.
Accordingly, it is an object of my invention
to provide a new and improved automatic regu
lation system for synchronous generators.
Another object of my invention is to provide
an automatic regulating system for alternating
current generators, for preventing excessive load
ing of the exciter driving means during system
disturbances.
‘
excitation is greatly reduced.
The invention will be better understood from
the following description taken in connection
with the accompanying drawings, and its scope
will be pointed out in the appended claims. In
the drawings, Fig. 1 illustrates diagrammatically
an embodiment of my invention showing a volt
age regulator with the exciter set slip limiting
55 feature; Fig. 2 is a modi?cation of the system as
9,478,629
3
-
.4
7
shown in Fig; i in which an amplidyne generator
thyrite will produce a disproportionately greater
is substituted for the rheostatic elementof the
voltage regulator for controlling the direct cur
rent exciter for the alternator, and Fig. 3 illus
trates several of the performance characteristics
of a motor driven exciter set operated in accord
ance with my invention.
?ow of current in the circuit, resulting in in
creased sensitivity and response of the circuit.
A standard source of direct current voltage is also
applied across the resistor I! as shown, and its
~ Referring now to the drawing and more par
value may be adjusted by means of a variable re
sistance I8.
The circuit as thus described pro- "
vides a voltage measuring or comparison circuit
ticularly to Fig. 1, I have shown a three phase
in which the output voltage of the recti?er, which
alternating current generator I connected to sup 10 is proportional to the slip of the induction motor,
ply power to a synchronous alternating current
is compared to a standard predetermined direct
system. The alternator is driven at synchronous
current vltage. At values of slip approaching the
speed by a prime mover shown as a ?uid pressure
value of ‘full load slip of the induction motor. the
turbine 2 and the alternator embodies the cus
‘voltage output of the recti?er will equal the '
tomary rotating ?eld construction having a ?eld 15 standard voltage and any increase in motor slip
winding 3 excited by a direct'current exciter I.
will cause an increased voltage to appear across
The direct current exciter l is mechanically driven
the resistor I6 and coil is. This excess voltage
by a polyphase induction motor 5 which receives.
is then eifective to cause a current ?ow in the
its electrical power from the output of the alter
bucking coil ii of the voltage regulator, thereby
nator I, or from the interconnected system for 20 reducing the net electromagnetic vforce available
starting purposes. The direct current exciter 4
to adjust the variable resistance 8 of the regulator
is provided with a shunt ?eld winding 6 in which _ and preventing the regulator from forcing the
the ?eld current is controlled by a voltage regu
output of the exciter to a higher value, with the
lator shown generally at ‘I. A variable resistance
result that the exciter load on the induction motor ‘
8 is in series with the shunt ?eld winding 6 and 25 is prevented from increasing to a value that would
effective to vary the exciter output and ?eld ex
overburden and seriously reduce the speed of the
citation of the alternator in response to system
induction 'motordrive.
voltage conditions, as will be more fully de
The voltage regulator ‘I may be of the direct
scribed.
‘
acting rheostatic type or of the carbon pile type
For obtaining "a direct. measurement of the 30 and is responsive to the output voltage of the al
value of slip in the induction motor exciter set,
ternator I by means of a voltage taken from the
a small three phase alternating current generator
terminals of the alternator by the conductors I9
9 of the tachometer or permanent magnet type
and passed through an adjusting resistance 20
is mechanically connected to the shaft of the
‘and a full-wave recti?er bridge 2|. The unidi
alternator I and, therefore, produces an alter
rectional output of the recti?er is then impressed
natin’g current frequency equal to that generated
on the operating coil 22 of the voltage regulator
by the main alternator I and supplied to the
‘I in such a direction as to actuate the regulator
induction motor 5. The output of the tachometer
generator 9 is applied to the three phase stator
mechanism which is balanced against a spring 30,
to e?ect a degrease in the value of resistance 8
winding of a conventional Selsyn receiver Ill. 40 and, therefore, increase the amount of excitation
The rotating single phase ?eld winding of the
supplied to the alternator I under conditions of
Selsyn I0 is mechanically connected to the shaft
decreasing terminal voltage of the alternator. A
of the induction motor 5, and, therefore, revolves
stabilizing transformer 23 is provided having one
at the same speed as the induction motor exciter
winding in parallel with the exciter output and
set and at a speed which di?ers from the rotating - the other winding in series with the voltage regu
?eld in the stator winding of the Selsyn ID by a
lator coil 22, 0s as to damp out any tendency oi
small value equal to the slip of the induction
the regulating circuit to oscillate.
motor, assuming that the proper pole ratio exists
For a better understanding of the operation
between the generator and induction motor, cor
of my invention, reference should now be made
responding to their synchronous speeds. As long 50 to Fig. 3. Curve A~of Fig. 3 shows the speed
as the induction motor is running under no load,
torque characteristic for a conventional induc
the value of the slip will be very low and the fre
' tion motor with rated applied voltage in which
quency and voltage output of the Selsyn rotor
the point of maximum or pullout torque is
will also be very low, however, as the slip of the
reached at a value of slip usually between 4
induction motor increases due to increased exciter
to 9 per cent, depending on the design and ap~
load, the differential speed between the rotating
plication of the motor. Curve A’ represents the
?eld in the stator of the Selsyn receiver and the
speed-load characteristic of the exciter 4 under
speed of the Selsyn rotor increases, thereby in
conditions of normal terminal voltage on the
creasing the voltage and the frequency output of
generator and with the regulator attempting to
the Selsyn rotor. The output of the Selsyn rotor 60 increase the exciter voltage to a maximum or
is tuned by means of the capacitance II, induct
ceiling value. It will be seen that the point m
ance I2 and shunting resistor I3 so that a maxi
at the intersection of the exciter load curve and
mum variation in voltage may be obtained in the
the motor torque curve indicates the value 01'
region of slip approaching the slip corresponding
slip at which the motor will operate when the
to the maximum electrical torque for the partic 65 exciter is supplying ceiling excitation and under
ular induction motor used.
conditions of rated terminal voltage on the in
The tuned output of the Selsyn rotor is applied
duction motor. If it is assumed that the ter
to the input terminals of a full-wave recti?er I 4
minal voltage supplied to the induction motor
which is preferably of the copper oxide type. The
decreases due to system disturbances, the char
output terminals of the recti?er M are connected w acteristic speed-torque curve of the induction
in series with the bucking coil I5 of the voltage
motor will be considerably reduced, as shown by
regulator, the ?xed resistance I6 and the thyrite
the curve B which represents the speed-torque
resistor IT. The thyrite resistor I1 has a non
characteristic of the motor when operating at
linear negative impedance voltage characteristic;
about 71 per cent of rated terminal voltage. It’
therefore, a slight increase in voltage across the 75 will be seen that the torque available from the
5
9,410,022
motor at any given speed at this reduced voltage‘
upon a decrease in alternator terminal voltage
is one-half the value available at rated voltage.
With the motor running at reduced voltage, the
and to decrease excitation upon an increase in
terminal voltage. A basic level of excitation is
load on the exciter will now almost equal the
provided for the amplidyne by the ?eld winding
value of maximum torque of the driving motor,
and any further reduction in motor terminal
voltage due to system conditions will decrease
the torque available from the induction motorto
22 in which a constant component of ?ux is pro
duced. This is supplied with energy from the
direct current source as shown and a variable
resistor 24 is provided to adjust this basic amount
of excitation for the amplidyne. For energizing
will pass the maximum torque point and quickly 10, the control ?eld 8 of the amplidyne, I have shown
a value less than the exciter load, and the motor
drop in speed with almost total loss of excitation
a positive phase sequence network shown gener
on the alternator.
ally at 20 and fully described and claimed in the
pending ‘application of Frederick E. Crever, Se
rial No. 538,933, ?led June 6, 1944, now Patent
2,407,476, issued September 10, 1946, and assigned
Since this condition of re
duced voltage on the driving motor has resulted
in a greater amount of slip of the motor, as rep—
resented by the point y, there has now been a
certain increase in slip and this is effective to
apply an increased bucking. ?ux in the coil l5
of the voltage regulator. The increase in slip
and consequent increase in bucking effect in the
to the same assignee as the present invention.
Also used in conjunction with the positive phase
sequence network is a nonlinear voltage sensitive
network shown. generally at 2|. _ The positive
regulator operates effectively to prevent any in 20 phase sequence network 20 provides a single
crease in the exciter load, and as the'value of
phase alternating current voltage value that is
slip increases the tendency of the regulator to
representative of the voltage condition existing
increase'exciter load is overcome and an actual
on all three phases of the generator I. This sin
reduction in exciter load is accomplished by the
gle phase voltage is applied to the nonlinear volt
proportionately greater increase in bucking ?ux
age sensitive network 2|, and the resulting re
in the regulator coil I5. Exciter load is reduced
due to the increased slip and the characteristic
versible direct current voltage is used to energize
the control ?eld 8 to produce a bucking or boost
speed-load curve of the exciter under conditions
of reduced terminal voltage on the driving motor
ing ?ux for the amplidyne generator 1. The
nonlinear voltage sensitive network includes a
reactor 25 and capacitor 28 in series circuit rela
tionship. The voltage appearing aorossthe ca
pacitor 28 is applied to a full-wave recti?er bridge
21, and the resultant direct current voltage out
and resultant increased slip is then represented
by the curve B’. The intersection of curves B
and B’ at point a then represents the point of
operation of the motor driven exciter set at re
duced voltage, and it can be seen that the induc
tion motor is now operating in a‘stable portion
put is compared with a source of voltage repre
sented by the battery 28 and the differential volt
age thus applied to the buck and boost control
of its speed-torque characteristic and will be pre
vented from reaching the maximum torque
point.
?eld 8. The ?xed resistor 29 is inserted across
the output terminals of the recti?er to permit
vthe flow of current in both directions which
otherwise would be prevented by the unidirec
tional characteristic of the recti?er 21. Thus
when the alternator voltage is low, the output
of the positive phase sequence network will be
low and the direct current voltage appearing
across the resistor 29 will be less than the volt
age of the battery 28. This will cause current
The load on the induction motor is,
therefore, automatically regulated at a safe value
and the motor-driven exciter set will be main
tained in a stable condition irrespective of a
large range of terminal voltage changes on the
induction motor drive. It will be understood
that the motor speed-torque curves A and B and
the corresponding exciter load curves A’ and B’
are merely representative of two values of motor
terminal voltage on the exciter set. For any
to ?ow in the control ?eld in a direction to pro
values or terminal voltage between 71 and 100
duce a boosting ?ux, thus raising the excitation
per cent, there will be a corresponding pair of
applied to the alternator l. Conversely, when
motor speed~torque curves and exciter load 50 the alternator voltage is higher than normal the
curves lying in the area between curves A and B,
direct current voltage appearing across the re
and A’ and B’, respectively. The slip responsive
sistor 28 from the rectifier bridge will be greater
circuit and associated bucking coil l5 in the reg
than the voltage of the battery and current will
ulator may be adjusted so that at any value of
?ow in the opposite direction in the control ?eld
slip, for example greater than that shown as
8, producing a bucking ?ux which is effective to
point z of Fig. 3, the voltage regulator will be
reduce the net excitation of the amplidyne and,
ineffective to increase exciter load. Any further
in turn, the excitation of the alternator I. The
particular circuit shown for the nonlinear volt
increase in slip due to further reduction in motor
terminal voltage will result in a, decrease in ex
age sensitive network 2| is not important in itself
citer output until stability is again restored at a 60 as there are a number of other equally satisfac
value of slip corresponding to point z of Fig. 3.
tory circuits which may be employed to produce
In the modi?cation shown in Fig. 2, I have
a direct current voltage of greater magnitude and
substituted for the conventional voltage regulator
1 an amplidyne-type 0f dynamo-electric machine
which may be, for example, of the compensated
armature reaction excited type as described and
claimed in U. S. Patent No. 2,227,992 issued upon
an application of M. A. Edwards and E. F. W.
variation than the applied variable alternating
current voltage. Any of these circuits may be
- used to provide the reversible current ‘flow for
Alexanderson and assigned to the assignee of
this invention. The amplidyne 1 is arranged to
be driven by the induction motor 5, and its out
put energizes the ?eld winding 6 of the exciter I.
The output of the amplidyne is controlled by a
buck and boost ?eld winding 8, the ?ux of which
is in a direction to provide increased excitation 75
energizing the buck and boost ?eld winding 8.
Thus for a decreasing terminal voltage, the po-,
larity of current ?ow in control ?eld 8 is in a
direction to produce a boosting flux, whereas for
a condition of increasing terminal voltage the
polarity is reversed and a bucking ?ux is pro
duced in the ?eld 8. This variable flux in ?eld
8, together with the constant ?ux in ?eld 22, com
bine to produce a net excitation ?ux in the am
Plidyne that is regulatory or alternator excita
acvacaa
,
7
tion in response to alternator terminal voltage.
lator ineffective to increase said generator’volt
Thus in the event of a fault or system disturb
age.
ance, the positive phase sequence voltages ap
pearing at the output terminals of the alternator
I will be reduced and the amplidyne will func
tion to increase excitation of the alternator,
thereby attempting to restore the alternator ter
minal voltage to its required value. A stabilizing
transformer 23 is provided, as in Fig. 1, to damp
out any tendency of the regulating circuit to hunt 10
or fall into oscillation.
As in Fig. 1, the slip frequency responsive cir
cuit of Fig. 2 is identical except that the result
ant direct current voltage, which is proportional
..
.
2. An automatic regulating system for a syn
chronous generator having a ?eld winding com
prising, in combination, an electric motor driven
exciter for supplying energizing current to said
?eld winding, a voltage regulator for said syn-'
chronous generator, and means non-linearly re
sponsive to the load on said electric motor for
IIlOdifYlIlg the action of said regulator to limit
the output of said exciter to a predetermined
maximum value below the maximum torque on
said motors.
'
3. An automatic regulating system for a syn
vto the slip frequency of the induction motor 5, 15 chronous generator comprising, in combination,
is applied to a bucking control ?eld l5 of the
amplidyne and is, therefore, effective to reduce
the net ?ux available for excitation of the ampli
dyne when a value of slip of the induction motor
corresponding to the predetermined allowable 20
a ?eld winding for said generator, a dynamo
electric exciter for supplying ?eld current to said
Fig. 2 is, therefore, similar to the apparatus dis
generator and arranged to be driven by an elec
tric motor, means responsive to the output volt
age of said generator for controlling said exciter
output, means responsive to speed variations of said
driving motor from a predetermined speed value,
and means actuated by said speed responsive
closed in Fig. 1 and operates in a similar manner,
means upon a predetermined - decrease in the
value has been reached.
,
The modi?cation of my invention as shown in
with. the exception that the alternator voltage 25 speed of said motor to render said voltage re
sensitive circuit shown in Fig. 2 is responsive
sponsive means ineffective to increase said exciter
output.
to the voltage condition existing on all three
phases of the regulated machine instead of sin
4. An automatic regulating system for an elec
gle phase response as shown in Fig. 1. With the
tric generator comprising, in combination, a ?eld
regulating system as herein described-it will be 30 winding forv said generator, a dynamo-electric
exciter for supplying energy to said ?eld winding,
understood that reliable apparatus has been pro
an induction motor for supplying driving power
vided ‘for controlling the excitation ofsynchro
nous generators when such generators are
to said exciter, means responsive to a voltage
condition of said generator for controlling the
equipped with a separate induction motor driven
exciter set. The exciter set slip control will op 35 output of said exciter to maintain said .generator
voltage constant, and means responsive to the
erate to maintain the-maximum amount of ex
value of slip of said induction motor and opera;
citation on the alternator that the exciter set is
tive to limit the maximum output of said exciter
capable of providing even during periods of low
upon attainment of a predetermined maximum '
voltage due to severe system faults or disturb
ances. Although excitation on the alternator 40 value of slip of said induction motor.
5. An automatic regulating system for an elec- '.
tric generator comprising, in combination, an
excitation supply system for said generator in
cluding a dynamo-electric machine driven by an
electric induction motor, means responsive to
generator voltage for varying the excitation of
said dynamo-electric machine to maintain con
stant said generator voltage, and means respon
motor drive, irrespective of input voltage ?uc
sive to the value of the slip of said induction
tuations on the induction motor. Therefore,‘ the
possibility of stalling the induction motor drive 50 motor for inversely varying the excitation of said
dynamo-electric machine, said voltage respon
due to excessive exciter load is minimized and
sive means being rendered ineffective by said slip
maximum utilization’ is made of the available
responsive means at a predetermined value of
power of the separately driven exciter set.
motor load.
.
While I have shown and described particular
6. An automatic regulating system for a syn
embodiments of~my invention, it will be obvious
chronous generator having a ?eld winding com
to those skilled in the art that changes and modi
prising, in combination, an excitation supply
?cations. may be made without departing from
system for said generator ?eld winding including
my invention in its broader aspects, and I, there
a direct current generator having a ?rst and a
fore, aim in the appended claims to cover all such
changes and modi?cations as fall within the true 00 second control ?eld windings, an electric induc
‘spirit and scope of my invention.
tion motor arranged to drive said direct current
generator, means responsive to a voltage condi
What I claim as new and desire to secure by
tion of said synchronous generator for varying
Letters Patent of the United States, is:
.
the excitation of said ?rst control ?eld winding,
1. An automatic regulating system for an elec-‘
65
and means responsive to the value of the slip of
tric ‘generator comprising, in combination, a ?eld
winding for said generator, a voltage regulator
said electric motor for varying the excitation of
for said generator, a dynamo-electric exciter for
said second control ?eld winding in opposition
supplying ?eld current to said generator and ar
to the excitation‘ on said ?rst control ?eld wind
ranged to be driven by an electric motor, means
ing and e?ective above a predetermined value
responsive to the load on said driving motor, 70 of slip to limit the output power of said direct
for limiting the operation of said voltage regu
current generator.
lator in increasing the voltage of said generator,
7. An automatic regulating system for a syn
may be reduced below that required for maxi
mum alternator output, su?lcient excitation may
be maintained to prevent the alternator from los
ing synchronism with the interconnected power
system. By means of my invention, the load on
the exciter is controlled so that it will never ex
ceed the available power output of its induction
1 said load responsive means being eii’ective upon
attainment of a predetermined value of load on
said driving motor to render said voltage regu
chronous generator comprising, in combination,
an excitation supply system for said generator
75 including an induction motor driven direct cur
2,478,822
.
9
‘
10
,
rent generator for supplying ?eld current to said
generator, a ?rst and second control-?eld wind
ings for said direct current generator and ar
ranged in opposition, means responsive to the
positive phase sequence voltages of said syn
chronous generator for varying the excitation
of said ?rst control ?eld winding, and means
responsive to the value of slip oi.’ said induction '
motor for varying the excitation of said second
control ?eld winding'and eiTective above a pre
determined value of motor slip to limit the load
on said inductor motor.
- an induction motor driven exciter for supplying
?eld current to said generator, output controlling
means for said exciter, generator voltage respon
sive means for adjusting said exciter output con
trolling means, means responsive to the value of
slip of said induction motor eilective to modify
said exciter output controlling means upon at
tainment of a predetermined value 01,’ slip 01 said '
motor, said‘ slip responsive means including dy
namo~electric apparatus for generating an elec
trical quantity proportional to the slip of said
motor, and means for producing a unidirectional
8. A ?eld excitation supply control system for
current disproportionate to the value of said elec
a synchronous generator comprising, in combina
trical quantity.
tion, a ?eld winding for said generator, 9. dyna 15
12. A load limiting regulator system for a mo
mo-electric machine for controlling the supply
tor driven generator set comprising an electric
of energy to said ?eld winding, a ?rst and a sec
generator for supplying energy to an external
ond control ?eld winding for said machine, an
circuit, excitation control means for said gener
induction motor for supplying driving power to
ator, a driving motor for ‘said generator, means
said machine, means responsive to the positive 20 responsive to speed variations of said driving mo
1 phase sequence voltages of said generator for in
tor from a predetermined speed value, and means
versely varying the excitation of said ?rst control
actuated abruptly by said speed responsive means
?eld winding to maintain constant said generator
upon a predetermined decrease in the speed of
output voltage, and means responsivev to the
said motor below said predetermined speed for
value of slip of said induction motor and effec 25 rendering said excitation control means ine?ec
‘tive in excess of a predetermined value of slip
tive to increase the said generator energy out
of said induction motor to energize said second
put.
.
control ?eld winding in a direction to oppose
13. A load limiting regulator system for a mo
the excitation of said ?rst control ?eld winding.
tor driven generator set comprising a generator
9. A ?eld excitation supply control system for 30 for supplying electrical energy to a variable load,
v a synchronous generator comprising, in combi
nation, a ?eld winding for said generator, a dy
namo-electric machine for supplying energy to
said ?eld winding, an induction motor for sup
excitation control means for said generator re
sponsive to an electrical condition of said-load,
an induction motor for driving said generator,
an alternating current supply for said induction
plying driving power to said machine, voltage 35 motor, and means responsive to a predetermined
regulating means responsive to the output voltage
value of slip of said induction motor and effec
of said generator for varying the‘ excitation of
tive to prevent said excitation control means
said machine to maintain constant said generator
from increasing said generator output.
output voltage, and means responsive to the value
14. A load limiting regulator system for a mo
of slip-oi’ said induction motor arranged to oppose
tor driven generator set comprising a generator
said voltage regulating means, said slip respon
for supplying electrical energy to a variable load,
sive means rendering said voltage responsive
excitation control means for said generator're
means ineffective to increase excitation of said
sponsive to an electrical condition of said load,
machine upon attainment of a predetermined
an induction motor- ior driving said generator, value of motor slip.
45 an alternating current supply for said induction
10. An.‘ automatic regulating system for a syn
motor, and means responsive to a predetermined
chronous generator comprising, in combination,
value of slip oi’ said induction motor and effec
‘an automatic voltage regulator for said generator,
tive to prevent said excitation control means
an induction motor driven exciter for supplying
from increasing said generator output, said slip
?eld current to said generator, and means re 50 responsive means including a dynamo-electric
sponsive to the value oi’ slip of said induction
machine arranged to be driven by said induction
motor and e?ective to limit ?eld excitation of said
motor for generating an electrical quantity di
generator upon attainment of a predetermined
recgy proportional to. the value of slip of said
value of slip of said motor, said slip responsive
mo
r.
means including dynamo-electric means for gen
erating a frequency output'proportional to the
slip of said motor, a tuned recti?er circuit for
producing a unidirectional current proportional
to said value of motor slip and means for apply
ing said unidirectional current to saidvoltage
regulator in a direction to limit generator voltage
increasing action of said regulator.
11. An automatic regulating system for a syn
chronous generator comprising, in combination,
SELDEN B. CRARY. ’
REFERENCES CITED
The following references are of record in the
?le of this patent:
UNITED STATES PATENTS
Number
Name
Date
795,462
Turbayne ....... -_ July 25, 1905 -
Certi?cate of Correction
Patent N0. 2,478,622
_
August 9, 1949
SELDEN B. CRARY
'
It is hereby certi?ed that errors appear in the printed speci?cation of the above
numbered‘ patent requiring correction as follows:
Column 4, line 12, for “vltage” read 'roltage; line 39, for “degrease” read decrease;
- line 46, for “0s” read so; column 8, line 13, for the word “motors” read motor‘1 col
umn 9, line 12, for “inductor” read induction;
and that the said Letters Patent should be read with these corrections therein that the
same may conform to the record of the case in the Patent O?ice.
Signed and sealed this 14th day of March,
D. 1950.
[M]
THOMAS F. MURPHY,
'
1
Assistant Commissioner of Patents. _
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